Phonograph needle comparator



April 3, 1956 1.. J. ANDRES 2,740,296

PHQNOGRAPH NEEDLE COMPARATOR Filed Dec. 11, 1952 i "4 PL/ W 59: fiwenzaz United States Patent 2,740,296 PHONOGRAPH'NEEDLE COMPARATOR vnew];xnataicncaga, 111:, assi ns. a nab; Incorporated, Chicago, 11]., acorporation Application December 11, 1952, Serial No. 325,479 1 Claim.(Cl. 73-432) This invention relates in general to phonographs and moreparticularly to a device for quickly testing the degree of Wear on theplaying tip of a phonograph needle Without removal from the tone arm.

Previous to this invention the generally accepted method for testing aphonograph needle required first the removal of the needle from thetransducer and then the visual examination of the playing point under arelatively powerful magnifier or microscope and comparing this pointwith an unworn needle or facsimile thereof. The removal of modernsub-miniature needles used in present day transducers is in itselfdifficult and the actual determination of wear by magnification requiresthe use of an expensive magnifier and is normally beyond theinterpretive ability of the average layman.

The testing comparator and method hereinafter described provides asimple yet effective means for interpreting wear of the playing tip ofthe needle well within the ability of the average layman without thenecessity of removing the needle from the transducer and constitutes theprincipal object of the invention.

A further object of the invention is the provision of a coated plateadapted to be placed on the stationary turntable of a phonograph forreceiving a test embossment from the needle in the phonograph transducerfor visual comparison with a standard embossment on the same plate.

These and other objects and advantages in one embodiment of theinvention are described and shown in the following specification anddrawing.

Fig. l is a plan view of a phonograph with a needle comparator intesting position on the turntable.

Fig. 2 is a full size plan view of the comparator.

Fig. 3 is a fragmentary enlarged cross sectional view of the comparatorshown Fig. 2 taken through section line 3-3.

Fig. 4 is an enlarged diagrammatic view illustrating the method ofmaking embossments with a new and a worn needle.

Fig. 5 is an enlarged fragmentary plan view showing the comparativeembossments made by a new and worn needle.

Fig. 1 illustrates a conventional phonograph having a turntable 1 and atone arm 2 and the needle comparator 3 placed on the turntable ready toreceive an embossment from the needle 4 in the tone arm 2.

Figs. 2 and 3 illustrate one embodiment of the comparator in which aplaten or transparent glass plate 5 having ordinary polished surfaces isheld in a paper board holder 6 sandwiched between upper and lower paperboard members 7 and 8 respectively. A notch 9 in one end of member 8 isused to register the comparator against the spindle of the turntable asshown in Fig. l.

A thin coating of opaque wax 10 is applied in intimate contact to oneouter surface of the glass plate 5 before assembly in the paper boardholder assembly 6, 7 and 8.

A preferred wax is a mixture of paraffin, carnauba and carbon black andmay be applied to the plate 5 by 2,740,296 lcfi Patented Apr. 3, i956mask'iri'g one outer surface ahddipping the plate in the melted wax and"permitting the plate to drain leaving a layer on on'e'sid'eapproximately .005 inch in' thicknes's'. Many'varieties of welt knownwaxes and lacquers are suitable for this' purpose as long as' they'remain reasonably softand free from embrittlemen t and ar'subst'antially opaque.

Referring to Fig. 1, a test embossment' is made by placing thecomparator 3 on the turntable as shown and manually positioning the tonearm with the needle point on the coated surface of the glass near thearrow 11 and then moving the arm about its vertical pivot across theplate, embossing a single groove in the wax coating. Previously orlater, a standard groove 12 is embossed with a new unworn needle on thesame plate for comparative purposes.

Referring to Fig. 4 needle point 13 represents a new needle with itsradiused point resting on the glass plate 5 and needle point 14represents a needle the same as 13 except having normal wear on itspoint from playing engagement with the record grooves. When each of theneedle tips thus illustrated are moved across the plate under normalneedle pressure, they will emboss grooves in the coating 10 and expose awidth of clear glass proportionate to the wear on the needle tips. Asillustrated, a new needle will expose clear glass of a width w whereas aworn needle will expose clear glass having a width W. Thus by holdingthe plate before good illumination a sharp distinction between the widthof the grooves is readily noted by the unaided eye. This comparisonwithout magnification is sufiicient to decide by predeterminedstandards, embossed on the plate or printed on the holder, whether ornot a needle requires replacement.

Although a variety of materials may be used for plate 5, glass wasselected because of its low cost availability and it is apparent thatthe surface of the glass plate 5 will not be embossed or otherwiseaffected by the needle tips because of its natural high finish andhardness.

Although the embossed lines lend themselves to good resolution with theunaided eye, it is also possible to use the same comparator constructionto permit the needle point to impress the coating without scribing andthus provide a transparent dot for comparative observation rather thanusing the groove method previously described. It is also apparent thatthe comparator may be positioned adjacent to the turntable for scribingwith the tone arm instead of on the turntable.

In the event a more accurate determination of small degrees of needlewear is required, then the lower side of glass plate 5 may be shaped inthe form of a cylindrical lens 15 (shown as dotted line Fig. 3) with itsradius of curvature and the image distance made equal. This alternateconstruction will magnify the embossments to the advantage of theobserver.

A contributing reason for the high resolving power of the abovedescribed comparator resides in the fact that spherical tipped needleswear fiat on their lowest extremity due to contact with the bottom ofthe record groove and since the plate 5 is positioned substantially inthe working position of the record, the lateral embossment on thesurface of the plate is a true representation of the above mentionedfiat.

Having thus described my invention, 1 claim:

A comparator for indicating the wear on the point of the needle in atone arm of a phonograph having a turntable comprising a flat platenmeans a portion of which is made of transparent glass and having asmooth planar upper surface, said upper surface coated with a thin layerof an opaque wax-like compound, there being a standard linear grooveengraved through said layer by the spherical point of an unworn needleproviding a transparent line at the bottom of said groove ofpredetermined width, means for. registering said platen on saidReferences Cited in the file of this patent turntahle when the latter isstationary so that said layer UNITED STATES PATENTS underlles thelateral movement of said needle in said 385 887 tone-arm and said groovelies in the same direction but Tamter July 1888 spaced from the actualpath of said needle in lateral move- 1'461849 JOPeS et a1 July 1923ment, whereby said tone arm needle may be tested by gig??? wfchart 1939manually drawing said needle across the wax-like layer 3 Clifton 1943 ofsaidplaten to produce a test groove, whereby the bot- OTHER REFERENCEStom width of said test groove when visually compared Phonofacts M Wen,Audio Engineering, June 1951' through said transparent glass with thebottom Width of 10 p 21. said standard groove will indicate the degreeof wear of said tone arm needle.

